A 400-year tree-ring chronology from the tropical treeline of North America.

High-elevation sites in the tropics may be particularly sensitive to rapid climate change. By sampling treeline populations, I have developed the first extensive (> 300 years) tree-ring chronology in tropical North America. The site is Nevado de Colima, at the western end of the Mexican Neovolcanic Belt, and the species studied is Mexican mountain pine (Pinus hartwegii). Despite past logging in the area, 300 to 500-year old pines were found at 3600-3700 m elevation, about 300 m below the present treeline. The Nevado de Colima tree-ring chronology is well replicated from 1600 to 1997. Calibration with Colima climatic records points to summer monsoon precipitation as the strongest dendroclimatic signal. Most trees also exhibit extremely low growth in 1913 and 1914, following the January 1913 Plinian eruption of the Volcan de Colima. Because P. hartwegii is found on top of high mountains from Mexico to Guatemala, there is potential for developing a network of tropical treeline chronologies.